There are already known designs of an explosive shell case with pre-shaped fragments, preferably in the form of balls of metal with high density, which are baked into a material surrounding the fragments which together with the fragments forms a connected jacket which surrounds the explosives of the shell. A case of this kind gives rise upon detonation of the explosive shell to fragments with small variation in weight and size. As a rule, use is made of balls of heavy metal consisting of 90-95 percent tungsten.
Explosive shell cases with pre-shaped fragments of heavy metal are, however, expensive, partly as a consequence of the content of heavy metal and partly as a consequence of the fact that the case is complicated to manufacture. Since the case must be able to absorb high pressures from the propellant charge and high centrifigal forces from the rotation of the shell, i.e. both axial and radial forces, exacting demands are imposed on its strength. At the same time, the case must also be so designed that the fragmentation effect of the shell becomes as effective as possible, in other words so that the fragments are accelerated to a high and uniform velocity.
Also already known is a method of manufacturing explosive shells in which the fragments are formed by bursting of the steel case of the shell. Explosive shells built up in this manner are, indeed, inexpensive and the fragmentation size is controllable to some extent by selection of material and heat treatment. It is nevertheless unavoidable that such explosive shells give rise to fragments of varying form, weight and size.